The role of endogenous digitalis-like factor in blood pressure regulation in essential hypertension

We examined plasma renin activity (PRA), plasma aldosterone (PA), atrial natriuretic factor (ANF) and endogenous digitalis-like factor (DLF) in 15 healthy subjects and 15 patients with essential hypertension (EH) to obtain basal values and values after extracellular fluid volume (ECFV) expansion caused by infusion of isotonic saline solution over a period of 2 hours (20 mg/kg). A significant increase in diuresis and natriuresis accompanied by a decrease in PRA and PA and an increase in ANF was observed in both groups. No significant differences were observed in ANF levels between normotensive subjects and hypertensive patients. Hypertensive patients showed significantly higher basal values of DLF than normotensive subjects. However, an increase in plasma DLF following ECFV expansion was observed only in the group of healthy subjects. There was a positive correlation between ANF and natriuresis and a negative correlation between ANF and systolic and diastolic blood pressure (BP). Changes in DLF correlated positively with changes in diastolic BP in both groups, while in healthy subjects a negative correlation was recorded between PRA and DLF. We conclude that the increased diuresis and natriuresis in ECFV expansion is presumably accounted for not only by suppression of PRA and PA, but also by stimulated ANF secretion, while in healthy subjects stimulation of DLF may be involved as well. The insufficient DLF response to saline infusion may indicate an exhausted DLF reserve in hypertensive patients. As a vasoactive substance, DLF can participate in the regulation of blood pressure and play a role in the pathogenesis of arterial hypertension.